Compact and extract functions in PHP - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the compact() function do in PHP?

The compact() function creates an array from variables and their values. You give it variable names as strings, and it returns an associative array where keys are the variable names and values are the variable values.

beginner

What is the purpose of the extract() function in PHP?

The extract() function imports variables into the current symbol table from an associative array. It creates variables named after the array keys and assigns them the corresponding values.

intermediate

How do compact() and extract() relate to each other?

compact() turns variables into an array, while extract() turns an array back into variables. They are like opposites and can be used to pass variables around easily.

intermediate

What happens if you use extract() with an array that has keys matching existing variables?

By default, extract() will overwrite existing variables with the same name. You can control this behavior with flags like EXTR_SKIP to avoid overwriting.

beginner

Show a simple example of using compact() and extract() together.

Example:<br>

$name = "Alice";<br>$age = 30;<br>$data = compact('name', 'age');<br>// $data is ['name' => 'Alice', 'age' => 30]<br>extract($data);<br>// Now $name and $age variables exist again with original values

What does compact('x', 'y') return if $x = 5 and $y = 10?

A Variables named 'x' and 'y' with values 5 and 10

B An array [5, 10]

C An array ['x' => 5, 'y' => 10]

D A string 'x y'

compact() returns an associative array with keys as variable names and values as their values.

What does extract(['a' => 1, 'b' => 2]) do?

A Deletes variables <code>$a</code> and <code>$b</code>

B Creates variables <code>$a = 1</code> and <code>$b = 2</code>

C Creates an array with keys 'a' and 'b'

D Returns an array [1, 2]

extract() creates variables named after the array keys with their corresponding values.

If you want to avoid overwriting existing variables when using extract(), which flag should you use?

A EXTR_OVERWRITE

B EXTR_IF_EXISTS

C EXTR_PREFIX_ALL

D EXTR_SKIP

EXTR_SKIP skips extracting variables if they already exist, preventing overwriting.

Which function would you use to turn variables into an associative array?

A compact()

B array_keys()

C array_merge()

D extract()

compact() creates an associative array from variables.

What will happen if you call extract() on an empty array?

A Nothing happens, no variables are created

B It throws an error

C It creates variables with null values

D It deletes all existing variables

If the array is empty, extract() does nothing and no variables are created.

Explain how compact() and extract() work and how they can be used together.

Think about turning variables into arrays and back.

What precautions should you take when using extract() in your code?

Consider variable conflicts and safety.