PHP isset() function
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.
<?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.
<?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
<!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 1Output
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 |