How to Extract Substring from a String in PHP?

Given a String, the task is to extract a substring from a string in PHP. Extracting substrings from a string is a common task in PHP, whether you need to extract a portion of text based on a specific position or find a substring based on a pattern. In this article, we will explore various approaches to extracting substrings from a string in PHP.

Approach 1: Using substr() Function

The substr() function is used to extract a substring from a string in PHP. It takes three arguments: the input string, the starting position (zero-based index), and optionally the length of the substring to extract.

<?php

$str = "Welcome to GeeksforGeeks";

$subStr = substr($str, 11, 13);

echo $subStr;

?>

GeeksforGeeks

Approach 2: Extracting Substring Before a Specific Character

To extract a substring that appears before a specific character or substring, you can use the strstr() function.

<?php

$str = "Welcome to GeeksforGeeks";

$subStr = strstr($str, 'G');

echo $subStr;

?>

GeeksforGeeks

Approach 3: Using Regular Expressions (Regex)

Regex provides a powerful way to extract substrings based on patterns. The preg_match() function can be used to extract substrings that match a specific regex pattern.

<?php

$str = "Welcome to GeeksforGeeks - A computer science portal";

if (preg_match('/to (.*?) -/', $str, $matches)) {
    echo $matches[1];
}

?>

GeeksforGeeks

Approach 4: Using explode() Function

The explode() function in PHP is used to split a string into an array based on a specified delimiter. By splitting the string and then accessing the desired element of the resulting array, you can effectively extract a substring.

Example: In this example, the string is split into an array of words using the space character as the delimiter. The third word (with zero-based index 2) is then accessed and printed.

<?php
// Sample string
$string = "Hello, this is an example string.";

// Split the string into an array using a space as the delimiter
$array = explode(" ", $string);

// Accessing the desired element
$substring = $array[2]; // Extracting "is"

echo $substring;

?>

is

Using mb_substr() Function

The mb_substr() function is used to extract a substring from a string, similar to the substr() function but specifically designed for multibyte character encodings. This function takes three arguments: the input string, the starting position (zero-based index), and optionally the length of the substring to extract.

Example

<?php
// Sample string
$string = "Hello, this is an example string.";

// Function to extract a word by its position using mb_substr
function getWordAtPosition($string, $wordPosition) {
    // Split the string into an array of words
    $words = explode(" ", $string);
    
    // Calculate the start position of the desired word
    $startPosition = 0;
    for ($i = 0; $i < $wordPosition; $i++) {
        $startPosition += mb_strlen($words[$i]) + 1; // +1 for the space delimiter
    }
    
    // Extract the desired word using mb_substr
    $wordLength = mb_strlen($words[$wordPosition]);
    $substring = mb_substr($string, $startPosition, $wordLength);
    
    return $substring;
}

// Extract the third word (zero-based index 2)
$substring = getWordAtPosition($string, 2); // Extracting "is"

echo $substring;

?>

Output

is