What is the usage of php empty()

php empty() function is used to check whether a variable is empty. The syntax of this function is "bool empty (mixed $var)", where the parameter "$var" represents the variable to be checked.

The operating environment of this article: windows7 system, PHP7.1 version, DELL G3 computer

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

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.

empty() After version 5.5, it supports expressions, not just variables.

Version requirements: PHP 4, PHP 5, PHP 7

Syntax

bool empty ( mixed $var )

Parameter description:

$var: Variable to be checked.

Note: Prior to PHP 5.5, empty() only supported variables; anything else would cause a parsing error. In other words, the following code will not work:

empty(trim($name))

Instead, you should use:

trim($name) == false

empty() and will not generate a warning, even if the variable does not exist. This means that empty() is essentially equivalent to !isset($var) || $var == false.

Return value

Returns FALSE when var exists and is a non-empty and non-zero value, otherwise returns TRUE.

The following variables will be considered empty:

"" (空字符串)
0 (作为整数的0)
0.0 (作为浮点数的0)
"0" (作为字符串的0)
NULL
FALSE
array() (一个空数组)
$var; (一个声明了，但是没有值的变量)

Example

<?php
$ivar1=0;
$istr1=&#39;Runoob&#39;;
if (empty($ivar1))
{
    echo &#39;$ivar1&#39; . " 为空或为 0。" . PHP_EOL;
}
else
{
    echo &#39;$ivar1&#39; . " 不为空或不为 0。" . PHP_EOL;
}
if (empty($istr1))
{
    echo &#39;$istr1&#39; . " 为空或为 0。" . PHP_EOL;
}
else
{
    echo &#39;$istr1&#39; . " 字符串不为空或不为0。" . PHP_EOL;
}
?>

The execution result is as follows:

$ivar1 为空或为 0。
$istr1 字符串不为空或不为0。

Recommended learning:《PHP video tutorial》

The above is the detailed content of What is the usage of php empty(). For more information, please follow other related articles on the PHP Chinese website!