PHP Looping

January 14, 2008 at 6:53 am · Filed under PHP Looping

Looping statements in PHP are used to execute the same block of code a specified number of times.

Looping

Very often when you write code, you want the same block of code to run a number of times. You can use looping statements in your code to perform this.

In PHP we have the following looping statements:

  • while – loops through a block of code if and as long as a specified condition is true
  • do…while – loops through a block of code once, and then repeats the loop as long as a special condition is true
  • for – loops through a block of code a specified number of times
  • foreach – loops through a block of code for each element in an array

The while Statement

The while statement will execute a block of code if and as long as a condition is true.

Syntax

while (condition)
code to be executed;

Example

The following example demonstrates a loop that will continue to run as long as the variable i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>
<?php 
$i=1;
while($i<=5)
  {
  echo "The number is " . $i . "<br />";
  $i++;
  }
?>
</body>
</html>

The do…while Statement

The do…while statement will execute a block of code at least once – it then will repeat the loop as long as a condition is true.

Syntax

do
{
code to be executed;
}
while (condition);

Example

The following example will increment the value of i at least once, and it will continue incrementing the variable i as long as it has a value of less than 5:

<html>
<body>
<?php 
$i=0;
do
  {
  $i++;
  echo "The number is " . $i . "<br />";
  }
while ($i<5);
?>
</body>
</html>

The for Statement

The for statement is used when you know how many times you want to execute a statement or a list of statements.

Syntax

for (initialization; condition; increment)
{
  code to be executed;
}

Note: The for statement has three parameters. The first parameter initializes variables, the second parameter holds the condition, and the third parameter contains the increments required to implement the loop. If more than one variable is included in the initialization or the increment parameter, they should be separated by commas. The condition must evaluate to true or false.

Example

The following example prints the text “Hello World!” five times:

<html>
<body>
<?php
for ($i=1; $i<=5; $i++)
{
  echo "Hello World!<br />";
}
?>
</body>
</html>

The foreach Statement

The foreach statement is used to loop through arrays.

For every loop, the value of the current array element is assigned to $value (and the array pointer is moved by one) – so on the next loop, you’ll be looking at the next element.

Syntax

foreach (array as value)
{
    code to be executed;
}

Example

The following example demonstrates a loop that will print the values of the given array:

<html>
<body>
<?php
$arr=array("one", "two", "three");
foreach ($arr as $value)
{
  echo "Value: " . $value . "<br />";
}
?>
</body>
</html>

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PHP Arrays

January 14, 2008 at 6:49 am · Filed under PHP Arrays

An array can store one or more values in a single variable name.

What is an array?

When working with PHP, sooner or later, you might want to create many similar variables.

Instead of having many similar variables, you can store the data as elements in an array.

Each element in the array has its own ID so that it can be easily accessed.

There are three different kind of arrays:

  • Numeric array – An array with a numeric ID key
  • Associative array – An array where each ID key is associated with a value
  • Multidimensional array – An array containing one or more arrays

Numeric Arrays

A numeric array stores each element with a numeric ID key.

There are different ways to create a numeric array.

Example 1

In this example the ID key is automatically assigned:

$names = array("Peter","Quagmire","Joe");

Example 2

In this example we assign the ID key manually:

$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";

The ID keys can be used in a script:

<?php
$names[0] = "Peter";
$names[1] = "Quagmire";
$names[2] = "Joe";
echo $names[1] . " and " . $names[2] . 
" are ". $names[0] . "'s neighbors";
?>

The code above will output:

Quagmire and Joe are Peter's neighbors

Associative Arrays

An associative array, each ID key is associated with a value.

When storing data about specific named values, a numerical array is not always the best way to do it.

With associative arrays we can use the values as keys and assign values to them.

Example 1

In this example we use an array to assign ages to the different persons:

$ages = array("Peter"=>32, "Quagmire"=>30, "Joe"=>34);

Example 2

This example is the same as example 1, but shows a different way of creating the array:

$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";

The ID keys can be used in a script:

<?php
$ages['Peter'] = "32";
$ages['Quagmire'] = "30";
$ages['Joe'] = "34";
echo "Peter is " . $ages['Peter'] . " years old.";
?>

The code above will output:

Peter is 32 years old.

Multidimensional Arrays

In a multidimensional array, each element in the main array can also be an array. And each element in the sub-array can be an array, and so on.

Example

In this example we create a multidimensional array, with automatically assigned ID keys:

$families = array
(
  "Griffin"=>array
  (
  "Peter",
  "Lois",
  "Megan"
  ),
  "Quagmire"=>array
  (
  "Glenn"
  ),
  "Brown"=>array
  (
  "Cleveland",
  "Loretta",
  "Junior"
  )
);

The array above would look like this if written to the output:

Array
(
[Griffin] => Array
  (
  [0] => Peter
  [1] => Lois
  [2] => Megan
  )
[Quagmire] => Array
  (
  [0] => Glenn
  )
[Brown] => Array
  (
  [0] => Cleveland
  [1] => Loretta
  [2] => Junior
  )
)

Example 2

Lets try displaying a single value from the array above:

echo "Is " . $families['Griffin'][2] . 
" a part of the Griffin family?";

The code above will output:

Is Megan a part of the Griffin family?

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PHP Switch Statement

January 14, 2008 at 6:42 am · Filed under PHP Switch Statement

The Switch statement in PHP is used to perform one of several different actions based on one of several different conditions.

The Switch Statement

If you want to select one of many blocks of code to be executed, use the Switch statement.

The switch statement is used to avoid long blocks of if..elseif..else code.

Syntax

switch (expression)
{
case label1:
  code to be executed if expression = label1;
  break;  
case label2:
  code to be executed if expression = label2;
  break;
default:
  code to be executed
  if expression is different 
  from both label1 and label2;
}

Example

This is how it works:

  • A single expression (most often a variable) is evaluated once
  • The value of the expression is compared with the values for each case in the structure
  • If there is a match, the code associated with that case is executed
  • After a code is executed, break is used to stop the code from running into the next case
  • The default statement is used if none of the cases are true
<html>
<body>
<?php
switch ($x)
{
case 1:
  echo "Number 1";
  break;
case 2:
  echo "Number 2";
  break;
case 3:
  echo "Number 3";
  break;
default:
  echo "No number between 1 and 3";
}
?>
</body>
</html>

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PHP If…Else Statements

January 12, 2008 at 5:23 am · Filed under PHP If...Else Statements

The if, elseif and else statements in PHP are used to perform different actions based on different conditions.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions.

You can use conditional statements in your code to do this.

  • if…else statement – use this statement if you want to execute a set of code when a condition is true and another if the condition is not true
  • elseif statement – is used with the if…else statement to execute a set of code if one of several condition are true

The If…Else Statement

If you want to execute some code if a condition is true and another code if a condition is false, use the if….else statement.

Syntax

if (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output “Have a nice weekend!” if the current day is Friday, otherwise it will output “Have a nice day!”:

<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!"; 
else
  echo "Have a nice day!"; 
?>
</body>
</html>

If more than one line should be executed if a condition is true/false, the lines should be enclosed within curly braces:

<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
  {
  echo "Hello!<br />"; 
  echo "Have a nice weekend!";
  echo "See you on Monday!";
  }
?>
</body>
</html>

The ElseIf Statement

If you want to execute some code if one of several conditions are true use the elseif statement

Syntax

if (condition)
  code to be executed if condition is true;
elseif (condition)
  code to be executed if condition is true;
else
  code to be executed if condition is false;

Example

The following example will output “Have a nice weekend!” if the current day is Friday, and “Have a nice Sunday!” if the current day is Sunday. Otherwise it will output “Have a nice day!”:

<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
  echo "Have a nice weekend!"; 
elseif ($d=="Sun")
  echo "Have a nice Sunday!"; 
else
  echo "Have a nice day!"; 
?>
</body>
</html>

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PHP Operators

January 12, 2008 at 4:37 am · Filed under PHP Operators

Operators are used to operate on values.

PHP Operators

This section lists the different operators used in PHP.

Arithmetic Operators

Operator Description Example Result
+ Addition x=2
x+2		 4
– Subtraction x=2
5-x		 3
* Multiplication x=4
x*5		 20
/ Division 15/5
5/2		 3
2.5
% Modulus (division remainder) 5%2
10%8
10%2		 1
2
0
++ Increment x=5
x++		 x=6
— Decrement x=5
x–		 x=4

Assignment Operators

Operator Example Is The Same As
= x=y x=y
+= x+=y x=x+y
-= x-=y x=x-y
*= x*=y x=x*y
/= x/=y x=x/y
.= x.=y x=x.y
%= x%=y x=x%y

Comparison Operators

Operator Description Example
== is equal to 5==8 returns false
!= is not equal 5!=8 returns true
> is greater than 5>8 returns false
< is less than 5<8 returns true
>= is greater than or equal to 5>=8 returns false
<= is less than or equal to 5<=8 returns true

Logical Operators

Operator Description Example
&& and x=6
y=3(x < 10 && y > 1) returns true
|| or x=6
y=3(x==5 || y==5) returns false
! not x=6
y=3!(x==y) returns true

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PHP String

January 12, 2008 at 4:34 am · Filed under PHP String

A string variable is used to store and manipulate a piece of text.

Strings in PHP

String variables are used for values that contains character strings.

In this tutorial we are going to look at some of the most common functions and operators used to manipulate strings in PHP.

After we create a string we can manipulate it. A string can be used directly in a function or it can be stored in a variable.

Below, the PHP script assigns the string “Hello World” to a string variable called $txt:

<?php
$txt="Hello World";
echo $txt;
?>

The output of the code above will be:

Hello World

Now, lets try to use some different functions and operators to manipulate our string.

The Concatenation Operator

There is only one string operator in PHP.

The concatenation operator (.)  is used to put two string values together.

To concatenate two variables together, use the dot (.) operator:

<?php
$txt1="Hello World";
$txt2="1234";
echo $txt1 . " " . $txt2;
?>

The output of the code above will be:

Hello World 1234

If we look at the code above you see that we used the concatenation operator two times. This is because we had to insert a third string.

Between the two string variables we added a string with a single character, an empty space, to separate the two variables.

Using the strlen() function

The strlen() function is used to find the length of a string.

Let’s find the length of our string “Hello world!”:

<?php
echo strlen("Hello world!");
?>

The output of the code above will be:

12

The length of a string is often used in loops or other functions, when it is important to know when the string ends. (i.e. in a loop, we would want to stop the loop after the last character in the string)

Using the strpos() function

The strpos() function is used to search for a string or character within a string.

If a match is found in the string, this function will return the position of the first match. If no match is found, it will return FALSE.

Let’s see if we can find the string “world” in our string:

<?php
echo strpos("Hello world!","world");
?>

The output of the code above will be:

6

As you see the position of the string “world” in our string is position 6. The reason that it is 6, and not 7, is that the first position in the string is 0, and not 1.

Complete PHP String Reference

For a complete reference of all string functions, go to our complete PHP String Reference.

The reference contains a brief description and examples of use for each function!

PHP String Functions

PHP String Introduction

The string functions allow you to manipulate strings.

Installation

The string functions are part of the PHP core. There is no installation needed to use these functions.

PHP String Functions

PHP: indicates the earliest version of PHP that supports the function.

Function Description PHP
addcslashes() Returns a string with backslashes in front of the specified characters 4
addslashes() Returns a string with backslashes in front of predefined characters 3
bin2hex() Converts a string of ASCII characters to hexadecimal values 3
chop() Alias of rtrim() 3
chr() Returns a character from a specified ASCII value 3
chunk_split() Splits a string into a series of smaller parts 3
convert_cyr_string() Converts a string from one Cyrillic character-set to another 3
convert_uudecode() Decodes a uuencoded string 5
convert_uuencode() Encodes a string using the uuencode algorithm 5
count_chars() Returns how many times an ASCII character occurs within a string and returns the information 4
crc32() Calculates a 32-bit CRC for a string 4
crypt() One-way string encryption (hashing) 3
echo() Outputs strings 3
explode() Breaks a string into an array 3
fprintf() Writes a formatted string to a specified output stream 5
get_html_translation_table() Returns the translation table used by htmlspecialchars() and htmlentities() 4
hebrev() Converts Hebrew text to visual text 3
hebrevc() Converts Hebrew text to visual text and new lines (\n) into <br /> 3
html_entity_decode() Converts HTML entities to characters 4
htmlentities() Converts characters to HTML entities 3
htmlspecialchars_decode() Converts some predefined HTML entities to characters 5
htmlspecialchars() Converts some predefined characters to HTML entities 3
implode() Returns a string from the elements of an array 3
join() Alias of implode() 3
levenshtein() Returns the Levenshtein distance between two strings 3
localeconv() Returns locale numeric and monetary formatting information 4
ltrim() Strips whitespace from the left side of a string 3
md5() Calculates the MD5 hash of a string 3
md5_file() Calculates the MD5 hash of a file 4
metaphone() Calculates the metaphone key of a string 4
money_format() Returns a string formatted as a currency string 4
nl_langinfo() Returns specific local information 4
nl2br() Inserts HTML line breaks in front of each newline in a string 3
number_format() Formats a number with grouped thousands 3
ord() Returns the ASCII value of the first character of a string 3
parse_str() Parses a query string into variables 3
print() Outputs a string 3
printf() Outputs a formatted string 3
quoted_printable_decode() Decodes a quoted-printable string 3
quotemeta() Quotes meta characters 3
rtrim() Strips whitespace from the right side of a string 3
setlocale() Sets locale information 3
sha1() Calculates the SHA-1 hash of a string 4
sha1_file() Calculates the SHA-1 hash of a file 4
similar_text() Calculates the similarity between two strings 3
soundex() Calculates the soundex key of a string 3
sprintf() Writes a formatted string to a variable 3
sscanf() Parses input from a string according to a format 4
str_ireplace() Replaces some characters in a string (case-insensitive) 5
str_pad() Pads a string to a new length 4
str_repeat() Repeats a string a specified number of times 4
str_replace() Replaces some characters in a string (case-sensitive) 3
str_rot13() Performs the ROT13 encoding on a string 4
str_shuffle() Randomly shuffles all characters in a string 4
str_split() Splits a string into an array 5
str_word_count() Count the number of words in a string 4
strcasecmp() Compares two strings (case-insensitive) 3
strchr() Finds the first occurrence of a string inside another string (alias of strstr()) 3
strcmp() Compares two strings (case-sensitive) 3
strcoll() Locale based string comparison 4
strcspn() Returns the number of characters found in a string before any part of some specified characters are found 3
strip_tags() Strips HTML and PHP tags from a string 3
stripcslashes() Unquotes a string quoted with addcslashes() 4
stripslashes() Unquotes a string quoted with addslashes() 3
stripos() Returns the position of the first occurrence of a string inside another string (case-insensitive) 5
stristr() Finds the first occurrence of a string inside another string (case-insensitive) 3
strlen() Returns the length of a string 3
strnatcasecmp() Compares two strings using a “natural order” algorithm (case-insensitive) 4
strnatcmp() Compares two strings using a “natural order” algorithm (case-sensitive) 4
strncasecmp() String comparison of the first n characters (case-insensitive) 4
strncmp() String comparison of the first n characters (case-sensitive) 4
strpbrk() Searches a string for any of a set of characters 5
strpos() Returns the position of the first occurrence of a string inside another string (case-sensitive) 3
strrchr() Finds the last occurrence of a string inside another string 3
strrev() Reverses a string 3
strripos() Finds the position of the last occurrence of a string inside another string (case-insensitive) 5
strrpos() Finds the position of the last occurrence of a string inside another string (case-sensitive) 3
strspn() Returns the number of characters found in a string that contains only characters from a specified charlist 3
strstr() Finds the first occurrence of a string inside another string (case-sensitive) 3
strtok() Splits a string into smaller strings 3
strtolower() Converts a string to lowercase letters 3
strtoupper() Converts a string to uppercase letters 3
strtr() Translates certain characters in a string 3
substr() Returns a part of a string 3
substr_compare() Compares two strings from a specified start position (binary safe and optionally case-sensitive) 5
substr_count() Counts the number of times a substring occurs in a string 4
substr_replace() Replaces a part of a string with another string 4
trim() Strips whitespace from both sides of a string 3
ucfirst() Converts the first character of a string to uppercase 3
ucwords() Converts the first character of each word in a string to uppercase 3
vfprintf() Writes a formatted string to a specified output stream 5
vprintf() Outputs a formatted string 4
vsprintf() Writes a formatted string to a variable 4
wordwrap() Wraps a string to a given number of characters 4

PHP String Constants

PHP: indicates the earliest version of PHP that supports the constant.

Constant Description PHP
CRYPT_SALT_LENGTH Contains the length of the default encryption method for the
system. For standard DES encryption, the length is 2
CRYPT_STD_DES Set to 1 if the standard DES-based encryption with a 2 character salt is supported, 0 otherwise
CRYPT_EXT_DES Set to 1 if the extended DES-based encryption with a 9 character salt is supported, 0 otherwise
CRYPT_MD5 Set to 1 if the MD5 encryption with a 12 character salt starting with $1$ is supported, 0 otherwise
CRYPT_BLOWFISH Set to 1 if the Blowfish encryption with a 16 character salt starting with $2$ or $2a$ is supported, 0 otherwise0
HTML_SPECIALCHARS
HTML_ENTITIES
ENT_COMPAT
ENT_QUOTES
ENT_NOQUOTES
CHAR_MAX
LC_CTYPE
LC_NUMERIC
LC_TIME
LC_COLLATE
LC_MONETARY
LC_ALL
LC_MESSAGES
STR_PAD_LEFT
STR_PAD_RIGHT
STR_PAD_BOTH

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PHP Variables

January 12, 2008 at 4:11 am · Filed under PHP Variables

Variables are used for storing values, such as numbers, strings or function results, so that they can be used many times in a script.

Variables in PHP

Variables are used for storing a values, like text strings, numbers or arrays.

When a variable is set it can be used over and over again in your script

All variables in PHP start with a $ sign symbol.

The correct way of setting a variable in PHP:

$var_name = value;

New PHP programmers often forget the $ sign at the beginning of the variable. In that case it will not work.

Let’s try creating a variable with a string, and a variable with a number:

<?php
$txt = "Hello World!";
$number = 16;
?>

PHP is a Loosely Typed Language

In PHP a variable does not need to be declared before being set.

In the example above, you see that you do not have to tell PHP which data type the variable is.

PHP automatically converts the variable to the correct data type, depending on how they are set.

In a strongly typed programming language, you have to declare (define) the type and name of the variable before using it.

In PHP the variable is declared automatically when you use it.

Variable Naming Rules

  • A variable name must start with a letter or an underscore “_”
  • A variable name can only contain alpha-numeric characters and underscores (a-Z, 0-9, and _ )
  • A variable name should not contain spaces. If a variable name is more than one word, it should be separated with underscore ($my_string), or with capitalization ($myString)

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PHP Syntax

January 12, 2008 at 4:04 am · Filed under PHP Syntax

You cannot view the PHP source code by selecting “View source” in the browser – you will only see the output from the PHP file, which is plain HTML. This is because the scripts are executed on the server before the result is sent back to the browser.

Basic PHP Syntax

A PHP scripting block always starts with <?php and ends with ?>. A PHP scripting block can be placed anywhere in the document.

On servers with shorthand support enabled you can start a scripting block with <? and end with ?>.

However, for maximum compatibility, we recommend that you use the standard form (<?php) rather than the shorthand form.

<?php
?>

A PHP file normally contains HTML tags, just like an HTML file, and some PHP scripting code.

Below, we have an example of a simple PHP script which sends the text “Hello World” to the browser:

<html>
<body>
<?php
echo "Hello World";
?>
</body>
</html>

Each code line in PHP must end with a semicolon. The semicolon is a separator and is used to distinguish one set of instructions from another.

There are two basic statements to output text with PHP: echo and print. In the example above we have used the echo statement to output the text “Hello World”.

Comments in PHP

In PHP, we use // to make a single-line comment or /* and */ to make a large comment block.

<html>
<body>
<?php
//This is a comment
/*
This is
a comment
block
*/
?>
</body>
</html>

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PHP Installation

January 12, 2008 at 4:00 am · Filed under PHP Installation

What do You Need?

This tutorial will not explain how to install PHP, MySQL, or Apache Server.

If your server supports PHP – you don’t need to do anything! You do not need to compile anything or install any extra tools  – just create some .php files in your web directory – and the server will parse them for you. Most web hosts offer PHP support.

However, if your server does not support PHP, you must install PHP. Below is a link to a good tutorial from PHP.net on how to install PHP5:

http://www.php.net/manual/en/install.php

Download PHP

Download PHP for free here: http://www.php.net/downloads.php

Download MySQL Database

Download MySQL for free here: http://www.mysql.com/downloads/index.html

Download Apache Server

Download Apache for free here: http://httpd.apache.org/download.cgi

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Introduction to PHP

January 12, 2008 at 3:57 am · Filed under Introduction

A PHP file may contain text, HTML tags and scripts. Scripts in a PHP file are executed on the server.

What You Should Already Know

Before you continue you should have a basic understanding of the following:

  • HTML / XHTML
  • Some scripting knowledge

If you want to study these subjects first, find the tutorials on our Home page.

What is PHP?

  • PHP stands for PHP: Hypertext Preprocessor
  • PHP is a server-side scripting language, like ASP
  • PHP scripts are executed on the server
  • PHP supports many databases (MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc.)
  • PHP is an open source software (OSS)
  • PHP is free to download and use

What is a PHP File?

  • PHP files may contain text, HTML tags and scripts
  • PHP files are returned to the browser as plain HTML
  • PHP files have a file extension of “.php”, “.php3”, or “.phtml”

What is MySQL?

  • MySQL is a database server
  • MySQL is ideal for both small and large applications
  • MySQL supports standard SQL
  • MySQL compiles on a number of platforms
  • MySQL is free to download and use

PHP + MySQL

  • PHP combined with MySQL are cross-platform (means that you can develop in Windows and serve on a Unix platform)

Why PHP?

  • PHP runs on different platforms (Windows, Linux, Unix, etc.)
  • PHP is compatible with almost all servers used today (Apache, IIS, etc.)
  • PHP is FREE to download from the official PHP resource: www.php.net
  • PHP is easy to learn and runs efficiently on the server side

Where to Start?

  • Install an Apache server on a Windows or Linux machine
  • Install PHP on a Windows or Linux machine
  • Install MySQL on a Windows or Linux machine

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