Extract numbers from a string in PHP

This article demonstrates how to extract numbers from a string in PHP.

1. Using `preg_replace()` function

The idea is to identify all non-numeric characters in a string, and replace them with an empty string (""). In PHP, this can be done using the preg_replace() function. You can use the regex \D+ or [^0-9]+ to match one or more non-numeric characters, which can be easily modified to extract any additional characters from the string (like +, -, ., ,):

<?php

$str = 'X:+2.15, Y:-1.50, Z:0';

var_dump(preg_replace('/\D+/', '', $str));

Output: string(5) "2151500"

var_dump(preg_replace('/[^0-9-\+\.,]+/', '', $str));

Output: string(5) string(13) "+2.15,-1.50,0"

Download Run Code

You can use the preg_match_all() function to get an array of all matches, as illustrated below. Here, \d+ matches one or more numeric characters.

<?php

$str = 'X:+2.15, Y:-1.50, Z:0';

preg_match_all('/\d+/', $str, $matches);

print_r($matches[0]);

Array

(

[0] => 2

[1] => 15

[2] => 1

[3] => 50

[4] => 0

)

preg_match_all('/(\+|-){0,1}\d+\.{0,1}\d*/', $str, $matches);

print_r($matches[0]);

Array

(

[0] => +2.15

[1] => -1.50

[2] => 0

)

Download Run Code

2. Using `filter_var()` function

PHP has a built-in function called filter_var() that filters a variable with a specified filter. The FILTER_SANITIZE_NUMBER_FLOAT filter removes all characters from the string except digits, plus, and minus, and optionally eE. This filter will also remove the decimal character (.) unless FILTER_FLAG_ALLOW_FRACTION flag is specified. You may also use the FILTER_SANITIZE_NUMBER_INT which also removes all characters from the string except digits and +/-, but doesn’t accept any flag.

<?php

$x = 'X:+2.15';

$result = filter_var($x, FILTER_SANITIZE_NUMBER_INT);

var_dump($result); // string(5) "+215"

$result = filter_var($x, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION);

var_dump($result); // string(5) "+2.15"

$y = 'Y:-1.50';

$result = filter_var($y, FILTER_SANITIZE_NUMBER_INT);

var_dump($result); // string(5) "-150"

$result = filter_var($y, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION);

var_dump($result); // string(5) "-1.50"

Download Run Code

Note that both the above solutions preserve all plus, minus, and decimal signs. For example, the string "X--5.2" returns "Y--5.2". For example,

<?php

$str = 'X--5.2++Y';

$result = preg_replace('/[^0-9-\+\.]+/', '', $str);

var_dump($result); // string(8) "--5.2++"

$result = filter_var($str, FILTER_SANITIZE_NUMBER_FLOAT, FILTER_FLAG_ALLOW_FRACTION);

var_dump($result); // string(8) "--5.2++"

Download Run Code

That’s all about extracting numbers from a string in PHP.

Extract numbers from a string in PHP

1. Using preg_replace() function

2. Using filter_var() function

Share this:

1. Using `preg_replace()` function

2. Using `filter_var()` function