<?php
$array["historico"][] = [
        "valor1" => 10,
        "valor2" => 15,
        "operador" => "*",
        "resultado" => 150
    ];
 
$array["historico"][] = [
        "valor1" => 50,
        "valor2" => 5,
        "operador" => "-",
        "resultado" => 45
    ];
 
foreach( $array["historico"] as $key => $value ){
    echo "{$value["valor1"]} {$value["operador"]} {$value["valor2"]} = {$value["resultado"]}\n";
}
 
 

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