How to leave only numbers in php string

2 methods: 1. Use for to traverse the string and splice the numeric characters into a substring in the loop body. The syntax is "for($i=0;$i

The operating environment of this tutorial: Windows 7 system, PHP version 8.1, DELL G3 computer

php string only Two ways to leave numbers

Method 1: Use the for statement is_numeric() ".=" string splicing

<?php
header("content-type:text/html;charset=utf-8");
function findNum($str) {
	$str = trim($str);
	if (empty($str)) {
		echo &#39;&#39;;
	}else{
		$result = &#39;&#39;;
		for ($i = 0; $i < strlen($str); $i++) {
			if (is_numeric($str[$i])) {
				$result .= $str[$i];
			}
		}
		var_dump($result);
	}
}
$str = &#39;0我是123456一段测试的字789符串0&#39;;
echo "原字符串：";
var_dump($str);
echo "过滤其他字符串后：";
findNum($str);
?>

Analyze the above code:

• Use a for loop to traverse the string $str

• Use is_numeric($ in the loop body str[$i]) Determine whether the $str[$i] character is a numeric character;

• If so, take it out and use ".=" is spliced ​​into a digital substring.

Look at the output:

Method 2. Use the preg_replace() function

<?php
$str =&#39;0我是123456一段测试的字789符串0&#39;;
$result = preg_replace("/[^0-9]/", "", $str);
echo $result;
?>

Analyze the key code above:

##preg_replace("/[^0-9]/", "", $str) means matching except 0 Characters other than numbers between ~9 and replace these characters with null characters, that is, delete these characters. Then only numeric characters are left, so the output result is:

preg_replace($pattern, $replacement, $subject [, $limit = -1 [, &$count ]])" means searching for the part matching pattern in the subject and replacing it with replacement; the optional parameter limit is used to set the maximum number of substitutions (the default value is -1, which can be unlimited).

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