How to determine whether a string is empty in php

3 judgment methods: 1. Use the "==" operator to determine whether the string is a null character. If it is a null character, it will be empty. The syntax is "string ==''"; 2. Use mb_strlen () Get the length of the string and determine whether the string length is equal to 0. If equal, it is empty. The syntax is "mb_strlen (string, character encoding) == 0"; 3. Use empty() to determine whether the string is empty. Syntax "empty(string variable)", if TRUE is returned, it will be empty.

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

php determines the string Multiple methods for whether it is empty

Method 1: Use the "==" operator to determine whether the string is an empty character

• If it is a null character, the string is empty

• If it is not a null character, the string is not empty

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
	if($str==&#39;&#39;){
		echo "字符串为空<br>";
	}else{
		echo "字符串不为空：".$str."<br>";
	}
}
f(&#39;&#39;);
f(&#39;123&#39;);
?>

Method 2: Use the mb_strlen() function to determine whether the string is empty

mb_strlen() function returns the length of the string and can handle Chinese strings length issue.

• If the length of the string obtained is equal to 0, the string is empty

• If the length of the string obtained is greater than 0, the string Not empty

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
	if(mb_strlen($str,"utf-8")==0){
		echo "字符串为空<br>";
	}else{
		echo "字符串不为空：".$str."<br>";
	}
}
f(&#39;&#39;);
f(&#39;1235&#39;);
?>

Method 3: Use the empty() function to determine whether the string is empty

## The #empty() function is used to check whether a variable is empty.

empty ( mixed $var )

empty() Determines whether a variable is considered empty. When a variable does not exist, or its value is equal to FALSE, then it is considered not to exist. empty() does not generate a warning if the variable does not exist.

<?php
header("Content-type:text/html;charset=utf-8");
function f($str){
	if(empty($str)){
		echo "字符串为空<br>";
	}else{
		echo "字符串不为空：".$str."<br>";
	}
}
f(&#39;&#39;);
f(&#39;hello&#39;);
?>

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