PHP insert elements before, between and after some array elements

Question

I've a multidimensional array of some arrays, in which the first values are ordered and included in a specific range.

Example:

A1=[[0,a],[3,b],[5,c],[6,a],[9,c]] 

in which A1[i][0] are in range (0,10)

How can I obtain an array where, if the first value (A1[i][0]) isn't a value present in the first array, e.g.

A1[i][0]==2

I insert an array with that value in the right position, with a specified second value (example A)?

Example of output i want:

A1=[[0,a],[1,A],[2,A],[3,b],[4,A],[5,c],[6,a],[7,A],[8,A],[9,c]]

Answer 1

This will help

$A1 = [[0,'a'],[3,'b'],[5,'c'],[6,'a'],[9,'c']];
foreach($A1 as $A2) $A3[] = $A2[0];//make a new array contain keys of the first array.
for($i=0;$i<=9;$i++){
    if(!in_array($i, $A3)){
        $A1[] = [$i, 'A']; //check if the key not exist, make a new array with key who does not exist.
    }
}
asort($A1);//sort the new element inside the array
print_r($A1);

output is,

[[0,a],[1,A],[2,A],[3,b],[4,A],[5,c],[6,a],[7,A],[8,A],[9,c]]