PHP provides a lot of functions for manipulation of string and array. Many times we need to convert a string into an array to perform operations. This article demonstrate details of different functions which can be used to convert a string into an array. The details and examples of each function are given below :

1. explode()

explode() is one of the most popular function which is generally used to split a string into an array on the basis of a string delimiter. The explode() function breaks a string into substrings on the basis of specified delimiter and returns an array of substrings.

Syntax : explode ($delimiter, $string, $limit)  

$delimiter : Specifies a string which is used as separator. (Required)

$string : Specify string which has to split.(Required)

$limit : An integer value, which defines the number of elements in the returned array.(Optional)

Different possible values for limit parameters are :

limit > 0 : The array contains the limit number of elements.

limit < 0 : The array contains all elements except the last-limit element.

limit = 0 : O is treated as 1, The array contains one element which is complete string.

Result : It returns an array of substrings split from the original string by delimiter. explode() returns false with empty delimiter(""). If a string does not contain the delimiter or with negative limit, It will return an empty array.

Note : Support for negative limits were added from PHP version 5.1.0

Example :

<?php
$string = "apple,orange,mango,pear";

echo "<pre>";

// without limit
echo "Without limit : <br>";
print_r(explode(',',$string));

// with 0 limit
echo "<br>With 0 limit : <br>";
print_r(explode(',',$string,0));

// with positive limit
echo "<br>With positive limit : <br>";
print_r(explode(',',$string,2));

// with negative limit 
echo "<br>With negative limit : <br>";
print_r(explode(',',$string,-1));

echo "</pre>";
?>

Output : 

2. str_split()

str_split() function is also used to split a string into an array. The function splits a string by each character as the default, if there is no value specified for split_length parameter.

Syntax :  str_split($string, $split_length)

$string : Specifies a string to split.(Required)

$split_length : An integer value which defines the length (Number of characters) of substring. Default value equals to 1.(Optional)

Result : str_split() also returns an array of substrings, split from the specified string. The length of each array element depends on the value passed as split_length. As default str_split() splits the string with length of 1 character.

If split_length is less than 1, the function will return FALSE.

If the split_length is equal or greater than the length of the string, the function will return the whole string as an only element.

Example :

<?php
$string = "Testing PHP functions";

// without split length
echo "Without split lenght : <br>";
print_r(str_split($string));

echo "<pre>";

// with split length
echo "<br>With split lenght : <br>";
print_r(str_split($string, 4));

$string = "Hello";

// with split length greater than string
echo "<br>With split length greater than string : <br>";
print_r(str_split($string,6));

echo "</pre>";
?>

Output : 

3. preg_split()

Just like above function preg_split() function also split a string into substrings on the basis of regular expression and return an array as a result.

Synatx : preg_split ($expression, $string, $limit, $flags)

$expression : A regular expression which is used as delimiter.(Required)

$string : Specifies a string to split.(Required)

$limit : An integer which defines the length of array elements.(Optional)

$flags : flags defines the types of matching performed.(Optional)

$flags can have the following values :

PREG_SPLIT_NO_EMPTY : With this flag the preg_split() prevents the empty string and only returns the non-empty string as a result.

PREG_SPLIT_DELIM_CAPTURE : With this flag, the function will capture and returns the substring matched in the parenthesized expression.

PREG_SPLIT_OFFSET_CAPTURE :  With this flag, the function returns an array of the match string with its respective offset in string.

Flags can also be used in combination using | (bitwise) operator.

Result : preg_split() also returns an array. If a limit parameter is specified, then only string split into specified limit length. limit with values -1, 0 or NULL defines "no limit", which is useful for specifying flags.

Note : On matching fails, the function return an array with single element which contains the whole string.

Example :

<?php
$string = "PHP is preprocessor hypertext";

echo "<pre>";
// split the phrase by any number of space characters,
// which include " ", \r, \t, \n and \f
print_r(preg_split("/[\s]+/", $string));

echo "<br>";
echo "If pattern not match : <br>"
print_r(preg_split("/\,/", $string));

echo "<br>";

// with Flags
print_r(preg_split('/ /', $string, -1, PREG_SPLIT_OFFSET_CAPTURE));

echo "<br>";

$string = "Test";
print_r(preg_split('//', $string, -1, PREG_SPLIT_NO_EMPTY));

echo "</pre>";
?>

Output :