Item relocation in the array key

Question

Good afternoon! Although I have researched the subject and searched in the documentation, I have not yet been able to come up with a solution to the following problem.. I have an array brought from the bank with titles and items.

The array comes to me as follows:

$a[0] = [
    "titulo" => "titulo1",
    "item" => "item 1",
];
$a[1] = [
    "titulo" => "titulo 2",
    "item" => "item 2",
];
$a[2] = [
    "titulo" => "titulo 2",
    "item" => "item 3",
];

My goal is to transform this array into a new one, with the items already relocated, example:

$limpo[0] = [
    "titulo" => "titulo1",
    "item" => "item 1",
];
$limpo[1] = [
    "titulo" => "titulo 2",
    "item" => "item 2",
    "item" => "item 3,
];

That is, the titles will not repeat themselves.

So far, I’ve assembled the code as follows..

foreach ($a as $key => $value) {

    if($key>0){
        $comparacao = ($a[$key-1]["titulo"]);   
        echo($comparacao."<br>");
    }

    if($key==0){
    $limpo[$key] = [
        "titulo" => $value['titulo'],
        "item" => $value['item']
    ];
    }else if($value["titulo"] != $comparacao){
        $limpo[$key] = [
        "titulo" => $value['titulo'],
        "item" => $value['item']
    ];
    }
    else if($value["titulo"] == $comparacao){

        //array_push($limpo[($key-1)]['item'], $value['item']);

        $limpo[($key-1)] = [
        "titulo" => $value['titulo'],
        "item" => $value['item']
    ];
    }
}

However, the moment you fall in ($value["titulo"] == $comparacao), the "item 3" is allocated in place of item 2, being as follows:

$limpo[0] = [
    "titulo" => "titulo1",
    "item" => "item 1",
];
$limpo[1] = [
    "titulo" => "titulo 2",
    "item" => "item 3",
];

Is there any way to push in the previous position? The snippet with commented push is returning an error by indicating the previous position..

Hugs.

Answer 1

You can use the title as the index of the array since they are unique. So it’s easy to test if the title already exists. If it exists add the item to an array, it creates the title. Ex.:

<?php

$limpo = [];

foreach ($array as $a) {
    $titulo = $a["titulo"];

    if (! isset($limpo[$titulo])) {
        $limpo[$titulo] = [
            "titulo" => $a["titulo"],
            "item" => [ $a["item"] ],  // cria uma array de items
        ];
    } else {
        $limpo[$titulo]["item"][] = $a["item"];  // adiciona item ao array
    }
}

/* print:

    [
    'titulo 1' => [
        'titulo' => 'titulo 1',
        'item' => ['item 1']
    ],
    'titulo 2' => [
        'titulo' => 'titulo 2',
        'item' => ['item 2', 'item 3']
    ]
]

*/

Code working...