What does empty mean in php

In PHP, empty means "empty". It is a built-in function used to check whether a variable is empty. The syntax is "empty($var)"; when a variable value is 0, the empty character String, "0.0", ""0"", NULL, FALSE, empty array, empty() considers this variable to be equal to empty.

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

empty means "empty".

empty() is a built-in function in PHP that determines whether a variable is "empty".

empty will also detect whether the variable is empty or zero. When a variable value is 0, empty() considers the variable to be equivalent to being empty, which is equivalent to not being set.

Example:

$id=0;
empty($id)?print "It's empty .":print "It's $id ."; 
//结果：It's empty .
print "<br>";
!isset($id)?print "It&#39;s empty .":print "It&#39;s $id .";
//结果：It&#39;s 0 .

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.

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:

• "" (empty string)

• 0 (0 as an integer)

• 0.0 (0 as a floating point number)

• "0" (0 as a string)

• NULL

• FALSE

• array() (an empty array)

• $ var; (a variable declared but without a value)

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;
}
?>

Output:

$ivar1 为空或为 0。
$istr1 字符串不为空或不为0。

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