How to detect whether a string is a number in php

Two detection methods: 1. Use the is_numeric() function to detect whether a string is a numeric string. The syntax is "is_numeric (string)". If TRUE is returned, it is, and vice versa. 2. Convert the string to a numeric type, and then compare the number with the original string to determine whether they are equal. The syntax is "strcmp((float)$str,$str)==0". If TRUE is returned, vice versa. no.

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

Method 1: Use is_numeric() The function detects that the

string contains only digits, 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 numeric string, otherwise returns FALSE. Note that float returns 1, which is TRUE. (i.e. can check both integers and decimals).

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

?>

Method 2: Cast type conversion and compare for equality

• By casting type, Convert the string to a numeric type

• Compare the number with the original string to see if they are equal

  If they are equal, the original string is a numeric string.

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
	$num=(float)$str;
	if (strcmp($num,$str)==0){
    	echo "$str 是数字字符串<br><br>";
	}
	else{
	    echo "$str 不是数字字符串<br><br>" ;
	}
}
f("3.14");
f("a678");
f("678");
f("23d5");
?>

Instructions:

1. Forced type conversion

Just add the target type enclosed in parentheses before the variable to be converted. The variable types allowed in the parentheses are as follows:

• (int), (integer): Conversion Integer type;

• (bool), (boolean): Convert to Boolean type;

• (float), (double), ( real): Convert to floating point type;

• (string): Convert to string type;

• (array): Convert to array Type;

• (object): converted to object type.

<?php
header(&#39;content-type:text/html;charset=utf-8&#39;);   
$str = &#39;123.456abc&#39;;
echo &#39;原变量 $str 的类型为：&#39;.gettype($str)."<br>";
$int = (int)$str;
echo &#39;变量 $int 的类型为：&#39; . gettype($int) . &#39;<br>&#39;;
$float = (float)$str;
echo &#39;变量 $float 的类型为：&#39; . gettype($float) . &#39;<br>&#39;;
$bool = (bool)$str;
echo &#39;变量 $bool 的类型为：&#39; . gettype($bool). &#39;<br>&#39;;
$arr = (array)$str;
echo &#39;变量 $arr 的类型为：&#39; . gettype($arr);
?>

2. strcmp() function

strcmp() function compares two strings.

strcmp(string1,string2)

Return value:	The function returns: 0 - If the two strings are equal < ;0 - if string1 is less than string2 >0 - if string1 is greater than string2

Recommended learning: "PHP Video tutorial》

The above is the detailed content of How to detect whether a string is a number in php. For more information, please follow other related articles on the PHP Chinese website!