Array search functions in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the PHP function in_array() do?

It checks if a value exists in an array and returns true if found, otherwise false.

beginner

How does array_search() differ from in_array()?

array_search() returns the key of the found value in the array, or false if not found, while in_array() returns only true or false.

beginner

What is the return value of array_search() if the searched value is not found?

It returns false to indicate the value is not present in the array.

intermediate

Explain the use of the third parameter in in_array() and array_search().

The third parameter is a boolean for strict checking. If true, the functions check both value and type (===). If false or omitted, only value is checked (==).

intermediate

What will array_search('5', [1, 2, 3, 5]) return with strict mode off and on?

With strict mode off (default), it returns the key 3 because '5' loosely equals 5.<br>With strict mode on, it returns false because string '5' is not identical to integer 5.

Which PHP function returns the key of a value in an array?

A array_search()

B in_array()

C array_key_exists()

D array_keys()

array_search() returns the key of the found value. in_array() returns true/false only.

What does in_array('10', [10, 20, 30]) return by default?

A 10

B false

C true

D null

By default, in_array() does loose comparison, so string '10' matches integer 10.

If array_search() does not find the value, what does it return?

A false

B -1

C null

D 0

array_search() returns false when the value is not found.

Which parameter controls strict type checking in in_array()?

A First parameter

B No parameter controls this

C Second parameter

D Third parameter

The third parameter is a boolean that enables strict type checking.

What will array_search(5, ['5'], true) return?

A 0

B false

C 1

D 5

With strict mode on, integer 5 is not identical to string '5', so it returns false.

Describe how to check if a value exists in an array and get its key in PHP.

Think about two functions: one for yes/no, one for key.

Explain the difference between loose and strict checking in PHP array search functions.

Consider how '5' and 5 compare with and without strict mode.