PHP isset is used to check whether the variable is set or not.The PHP isset() function returns false if variable contains a NULL value.
Syntax:
isset(variable1, variable2….)
Presentation of PHP isset:
- In the above diagram, the isset variable is null so it will return false.
- In the above diagram, the isset variable is 10, and it will return true. It means if the variable is set and not null, then the isset() function will return true.
Example (Null Variable):
<?php
$var=null;
if(isset($var))
{
echo "True";
}
else{
echo "False";
}
?>
Output:
False
- In the above example, the variable is null, and it will return the false result.
Example (Not NullVariable):
<?php
$var=2;
if(isset($var))
{
echo "True";
}
else{
echo "False";
}
?>
Output:
True
- In the above example, the variable has 2 value, and it will return true
Example:
<!DOCTYPE html>
<html>
<head>
<style>
.error {color: #FF0000;}
</style>
</head>
<body>
<?php
//define variables and set to empty values
$genderEr = "";
$gender = "";
if ($_SERVER["REQUEST_METHOD"] == "POST")
{
if (empty($_POST["gender"]))
{
$genderEr = "Gender is required";
}
else
{
$gender = test_input($_POST["gender"]);
}
}
functiontest_input($data)
{
$data = trim($data);
$data = stripslashes($data);
return $data;
}
?>
<form method="post" action="<?php ($_SERVER["PHP_SELF"]);?>">
Gender:
<input type="radio" name="gender" <?php if (isset($gender) && $gender=="female");?> value="female">Female
<input type="radio" name="gender" <?php if (isset($gender) && $gender=="male") ;?> value="male">Male
<input type="radio" name="gender" <?php if (isset($gender) && $gender=="trans");?> value="trans">TransGender
<span class="error">* <?php echo $genderEr;?></span>
<br><br>
<input type="submit" name="submit" value="Submit">
</form>
</body>
</html>
- In the above example, the PHP isset() function is to check the variable ($gender) is set or not with a value( “female, male and trans”).
PHP isset Examples
Example 1
Output
10 is set with isset function
Example 2
Output
Specified array is not set.
Example 3
Output
bool(true)
bool(true)
Example 4
Output
bool(false)
bool(true)
isset vs. empty vs. is_null :
- isset() is to check if a variable is set with a value.
- empty() is to check if a given variable is empty.
- is_null() – It is to check whether a variable is defined as NULL.
| Functions |
“” |
Null |
False |
Undefined |
0 |
| isset() |
True |
False |
True |
False |
True |
| empty() |
True |
True |
True |
True |
True |
| is_null() |
False |
True |
False |
Error |
False |
