How to extract numbers from a string in PHP

This article demonstrates how to extract numbers from a string in PHP using various methods such as regex (regular expressions), built-in functions like `preg_match_all`, `filter_var`, and manual approaches.

Extracting numbers from a string is a common task when handling input data. This article will showcase different ways to extract numbers from a string in PHP, including using regular expressions (regex) and PHP's built-in functions.

PHP Code

Method 1: Using preg_match_all with regex

<?php
$string = "The price is 200 dollars and 30 cents.";
// Use regex to find all numbers in the string
preg_match_all('!\d+!', $string, $matches);

// Return an array containing all extracted numbers
print_r($matches[0]);
?>

Method 2: Using filter_var with FILTER_SANITIZE_NUMBER_INT

<?php
$string = "The price is 200 dollars and 30 cents.";
// Filter the string to keep only the integers
$numbers = filter_var($string, FILTER_SANITIZE_NUMBER_INT);

// Print the filtered numbers
echo $numbers;
?>

Method 3: Manually extracting numbers

<?php
$string = "The price is 200 dollars and 30 cents.";
// Loop through each character and extract numbers
$numbers = '';
for ($i = 0; $i < strlen($string); $i++) {
    if (is_numeric($string[$i])) {
        $numbers .= $string[$i];
    }
}

// Print the extracted numbers
echo $numbers;
?>

Detailed explanation:

Method 1: preg_match_all

1. preg_match_all('!\d+!', $string, $matches);: Uses regular expression to find all numeric sequences in the string.
2. print_r($matches[0]);: Prints an array of all the found numbers.

Method 2: filter_var

1. filter_var($string, FILTER_SANITIZE_NUMBER_INT);: Strips out all non-numeric characters from the string, leaving only integers.

Method 3: Manual approach

1. for ($i = 0; $i < strlen($string); $i++): Loops through each character in the string.
2. if (is_numeric($string[$i])): Checks if the current character is a digit.
3. echo $numbers;: Prints the extracted numbers.

System requirements:

• PHP version 7.0 or higher.

Tips:

• When working with strings that contain both numbers and non-numeric characters, always validate input to avoid unexpected data errors.
• If your string contains negative or floating-point numbers, consider adjusting the regular expression or method to accommodate them.