How to insert an element in any position in php

[JoneS_vbulletin3_import17818]

I am with an array like \[code\]$x = array(1,2,3,4,5);\[/code\] i would like to add element 6 in between 3 and 4 and make it like \[code\]array(1,2,3,6,4,5);\[/code\]how do i make it in that place or first place?