How to detect if a string only contains numbers in php

Two methods: 1. Use is_numeric() to detect whether a string is a numeric string, the syntax is "is_numeric (string)", if TRUE is returned, it only contains numbers. 2. Use preg_replace() with regular expressions to filter characters, return numeric characters, and form a numeric string. Use "===" to compare whether the numeric string and the original string are equal. If they are equal, they only contain digits. The syntax "preg_replace( "/[^0-9]/","",string)====string".

The operating environment of this tutorial: windows7 system, PHP version 8.1, DELL G3 computer

php detection string Two methods to determine whether it contains only numbers:

Method 1: Use the is_numeric() function to detect if the

string contains only numbers, then the String is a numeric string.

The is_numeric() function can detect whether a string is a numeric string.

is_numeric ($var)

• $var: Variable to be detected.

Returns TRUE if the specified variable $var is a number or a string of numbers, otherwise returns FALSE

<?php
header("Content-type:text/html;charset=utf-8");
$str1="a678";
$str2="678";
$str3="3.14";
if (is_numeric($str1)){
    echo "$var_name1 是数字字符串<br><br>";
}
else{
    echo "$str1 不是数字字符串<br><br>" ;
}
if (is_numeric($str2)){
    echo "$str2 是数字字符串<br><br>";
}
else{
    echo "$str2 不是数字字符串<br><br>";
}
?>

Method 2: Use the preg_replace() function and the "===" operator to detect

• Use the preg_replace() function with regular expressions to filter characters , returns numeric characters to form a numeric string

• Use the "===" operator to compare whether the numeric string and the original string are equal. If they are equal, the string only contains digits

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
	$result = preg_replace("/[^0-9]/", "", $str);
	if($result===$str){
    	echo "$str 字符串中只含数字<br><br>";
	}
	else{
	    echo "$str 字符串中还有其他字符<br><br>" ;
	}
}

f("a678");
f("678");
?>

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

Description: The preg_replace function performs a regular expression search and replacement. It is a powerful string replacement processing function. Its syntax format is

preg_replace($pattern, $replacement, $subject [, $limit = -1 [, &$count]])

Search for the part matching pattern in subject and replace it with replacement.

Parameter description:

• $pattern: The pattern to be searched, which can be a string or a string array.

• $replacement: String or array of strings used for replacement.

• $subject: The target string or string array to be searched and replaced.

• $limit: Optional, the maximum number of substitutions for each subject string per pattern. The default is -1 (no limit).

• $count: Optional, the number of times the replacement is performed.

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