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How to check whether a variable is set or not in PHP
Topic: PHP / MySQLPrev|Next
Answer: Use the PHP isset() function
You can use the PHP isset() function to test whether a variable is set or not. The isset() will return FALSE if testing a variable that has been set to NULL.
Let's check out an example to understand how this function basically works:
Example
Try this code »<?php
$var1 = '';
if(isset($var1)){
echo 'This line is printed, because the $var1 is set.';
}
echo "<br>";
$var2 = 'Hello World!';
if(isset($var2)){
echo 'This line is printed, because the $var2 is set.';
}
echo "<br>";
// Unset the variable
unset($var2);
if(isset($var2)){
echo 'This line is printed, because the $var2 is set.';
} else{
echo 'This line is printed, because the $var2 is not set.';
}
echo "<br>";
$var3 = NULL;
if(isset($var3)){
echo 'This line is printed, because the $var3 is set.';
} else{
echo 'This line is printed, because the $var3 is not set.';
}
?>Related FAQ
Here are some more FAQ related to this topic:
- How to check whether a variable is empty in PHP
- How to check whether a variable is null in PHP
- How to check if a value exists in an array in PHP
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