# minte9 LearnRemember

### Map, Walk

Apply a user function to every member of an array.
``````
/**
* array_map, array_walk()
*
* Array walk needs reference
*/

function cube(\$n)
{
return pow(\$n, 3);
}

\$A = [1, 2, 3];
\$B = [1, 2, 3];
\$C = [1, 2, 3];
\$D = [1, 2, 3];

\$A = array_map('cube', \$A);
\$B = array_map(fn(\$x) => pow(\$x, 3), \$B);

array_walk(\$C, fn(&\$x) => \$x = pow(\$x, 3));
array_walk(\$D, fn(&\$x) => \$x *= 2); // Look Here

print_r(\$A); // 1 8 27
print_r(\$B); // 1 8 27
print_r(\$C); // 1 8 27
print_r(\$D); // 2 4 6
``````

### Next

We can use internal pointer when working with arrays.
``````
/**
* Reset, key, next, current ...
*/

\$arr = ['a'=>1, 'b'=>2, 'c'=>3];

reset(\$arr);
while (key(\$arr) !== NULL) {
print_r( key(\$arr) . current(\$arr) . " " ); // a1 b2 c3
next(\$arr);
}
``````

### Exists

Check to see if array exists or not.
``````
/**
* Check if array exists
* Use is_array() / not count()
*/

\$a = array();

echo count(\$a); // 0
echo is_array(\$a); // true
``````

Last update: 321 days ago