create a grouped array from another array - php

Question

I have a big array (read from a file)
$data = array(
array(134, 'Field_A_134', 'Field_B_134'),
array(134, 'Field_C_134', 'Field_D_134'),
array(134, 'Field_E_134', 'Field_F_134'),
array(180, 'Field_A_180', 'Field_B_180'),
array(70, 'Field_A_70', 'Field_B_70'),
array(180, 'Field_C_180', 'Field_D_180'),
...
);
and i want to group into another array by the first key from the first array (ex: 134, 180, 70, ...). Those keys are repeating, but the fields are different.
The array i want to make is:
array(
'134' => array(array(134, 'Field_A_134', 'Field_B_134'), array(134, 'Field_C_134', 'Field_D_134'), array(134, 'Field_E_134', 'Field_F_134')),
'180' => array(array(180, 'Field_A_180', 'Field_B_180'), array(180, 'Field_C_180', 'Field_D_180')),
'70' => array(array(70, 'Field_A_180', 'Field_B_180'))
);
Each key contains an array of arrays that contain the first key.
I was trying to make this:
$f = array();
$pr = array();
foreach($data as $p){
if(isset($f[$p[0]])){
array_push($f[$p[0]], $p);
} else {
$f[$p[0]] = $p;
}
array_push($pr, $f);
}
but it`s not what i want.

Answer 1

The error is in the else part. You need to assign an array, like this:
$f[$p[0]] = [$p];
Or like this, since PHP will create the array on the fly:
$f[$p[0]][] = $p;
And since that code can also be used when the array already exists, you can simplify to this loop:
foreach($data as $p) {
$f[$p[0]][] = $p;
}