Examining variable types in PHP

In PHP, there are a range of built-in functions which you can call to check variable types.  They return a Boolean value  – true if the variable is of that type and false if it is not.

To check if a variable contains a string, you can use the is_string function. You can use it like that:

echo var_dump(is_string("DQDQ")); // true

echo var_dump(is_string(23)); // false

echo var_dump(is_string("11")); // true

You should be aware that a number within a string (for example, coming from user input) is still a string and not a number when checking the variable type.

To check whether a variable is an integer, you can use the is_int function.

echo var_dump(is_int("11")); //false

echo var_dump(is_int(11)); //true

The point here is that strings with integers in them will result in a falsey return value.

To simply check whether a variable holds a numeric value, you can use the is_numeric function.

You can simply check if the variable holds a numeric value, no matter of the data type with the help of the is_numeric function.

echo var_dump(is_numeric("11")); // true

echo var_dump(is_numeric(11)); // true

echo var_dump(is_numeric("dqdq")); // false

echo var_dump(is_numeric("1123.23")); // true

The function will return true if the value contains an integer or a float, regardless of whether it is a string or of a numeric data type.

To check if a variable contains a floating point number, you can use the is_float method.

echo var_dump(is_float("11")); // false

echo var_dump(is_float(11.23)); // true

echo var_dump(is_numeric("word")); // false

echo var_dump(is_float("1123.23")); // false

The function will return true only if the variable contains a floating point number, strings excluded.

To check if the variable contains an array, you can use the is_array($var) function.

Similarly, to check if a variable is an object, you can use the is_object function. Here is a simple example:

<?php

class myClass {

                public function __construct($age) {

                $this->age = 26;

                }

}

$myLife = new myClass(26);

echo var_dump(is_object($myLife));

You can also use the is_bool function to check for Booleans, it checks for the data type so a string holding a Boolean would not count.

echo var_dump(is_bool("true")); //false

echo var_dump(is_bool(false)); //true

You can also use the class_exists function to check if a class exists:

class myClass {

                public function __construct($age) {

                $this->age = 26;

                }

}

echo var_dump(class_exists("myClass"));

You can give it a string with the expected name of the class.

You can use the instance of operator check if a variable contains an instance of a given class. Here is an example:

<?php

class myClass {

                public function __construct($age) {

                $this->age = $age;

                }

}

$me = new myClass(26);

echo var_dump($me instanceof myClass);