How to implement the function of taking only numbers in php

How to implement php to only take numbers: 1. Use the "preg_match" function to extract numbers from the string; 2. Use PHP's built-in "in_array" method to extract all the numbers that appear in the string. And spliced ​​together; 3. Use the "is_numeric" method.

php Extract numbers from the string

1. Regular extraction [Only extract the first occurrence Numbers]

<?php
$str =&#39;我是123456一段测试的字789符串00&#39;;
preg_match(&#39;/\d+/&#39;,$str,$number);
print_r($number);
?>

2. Regular extraction [All numbers appearing in the string are extracted in array form]

<?php
$str =&#39;我是123456一段测试的字789符串00&#39;;
preg_match_all(&#39;/\d+/&#39;,$str,$arr);
print_r($arr);
?>

3. Use in_array Method [Extract all the numbers that appear in the string and splice them together in string form] Pay attention to the encoding issue

$str='我是123456一段测试的字789符串00';
$str=trim($str);
if (!empty($str)) {
    $key    = ['0','1','2','3','4','5','6','7','8','9'];
    $number = '';
    for ($i = 0;$i < strlen($str);$i++) {
        if (in_array($str[$i],$key)){
            $number .= $str[$i];
        }
    }
}
print_r($number);

4. Use the is_numeric method like the in_array method

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