How to Use preg_split in PHP: Syntax and Examples

In PHP, preg_split splits a string into an array using a regular expression pattern as the delimiter. You provide the pattern and the string, and it returns an array of substrings separated by matches of the pattern.

Syntax

The preg_split function has this syntax:

• preg_split(string $pattern, string $subject, int $limit = -1, int $flags = 0): array|false

Here:

• $pattern: The regular expression pattern to split by.
• $subject: The input string to split.
• $limit: Maximum number of splits; default is no limit.
• $flags: Optional flags to modify behavior (like PREG_SPLIT_NO_EMPTY to remove empty parts).

php

array|false preg_split(string $pattern, string $subject, int $limit = -1, int $flags = 0);

Example

This example splits a sentence into words using spaces and commas as separators.

php

<?php
$text = "apple, banana orange,grape";
$parts = preg_split('/[ ,]+/', $text);
print_r($parts);
?>

Output

Array
(
    [0] => apple
    [1] => banana
    [2] => orange
    [3] => grape
)

Common Pitfalls

Common mistakes include:

• Using a pattern without delimiters (like slashes /pattern/), which causes errors.
• Not escaping special regex characters in the pattern.
• Ignoring empty strings in the result when multiple delimiters appear consecutively.

Use PREG_SPLIT_NO_EMPTY flag to avoid empty parts.

php

<?php
// Wrong: missing delimiters
// $result = preg_split('[,]', 'a,b,c'); // Causes warning

// Right: with delimiters
$result = preg_split('/,/', 'a,b,c');
print_r($result);

// Handling empty parts
$text = 'a,,b';
// Without flag
print_r(preg_split('/,/', $text));
// With flag to remove empty
print_r(preg_split('/,/', $text, -1, PREG_SPLIT_NO_EMPTY));
?>

Output

Array
(
    [0] => a
    [1] => b
    [2] => c
)
Array
(
    [0] => a
    [1] => 
    [2] => b
)
Array
(
    [0] => a
    [1] => b
)

Quick Reference

Parameter	Description
$pattern	Regular expression pattern with delimiters to split by
$subject	Input string to split
$limit	Maximum number of splits (-1 means no limit)
$flags	Optional flags like PREG_SPLIT_NO_EMPTY to remove empty results

Key Takeaways

Use preg_split to split strings by regex patterns in PHP.

Always include delimiters (like slashes) around your regex pattern.

Use PREG_SPLIT_NO_EMPTY flag to avoid empty strings in the result.

The $limit parameter controls how many splits to perform.

Check your regex pattern carefully to avoid unexpected splits.