Use if inside foreach

Question

I’m trying to change the order in which the results appear within a loop using foreach. What I need is for the numbers larger than five to appear first, followed by the rest of the numbers. So I tried something like this:

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
echo '<ul>';
foreach($numeros as $numero){
    if($numero > 5){
        echo '<li>'.$numero.'</li>';
    }else{
        echo '<li>'.$numero.'</li>';
    }
}
echo '</ul>';

But it’s not working.

Answer 1

I answered only to illustrate what is happening. What happens in your code, is that you have created a condition that can be read like this:

1. Itere in all elements
2. If larger than five, print.
3. otherwise, print.

Then they all appear. Try this code, with the same problem, but with a "hint" inside the if to understand what happened:

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
echo '<ul>';
foreach($numeros as $numero){
    if($numero > 5){
        echo '<li>MAIOR QUE CINCO - '.$numero.'</li>';
    }else{
        echo '<li>MENOR OU IGUAL - '.$numero.'</li>';
    }
}
echo '</ul>';

A simplistic solution would be to separate the loops (still didactically, because in the practical case, we would probably have much better solutions):

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
echo '<ul>';
foreach($numeros as $numero){
    if($numero > 5){
        echo '<li>'.$numero.'</li>';
    }
}
foreach($numeros as $numero){
    if($numero <= 5) {
        echo '<li>'.$numero.'</li>';
    }
}
echo '</ul>';

We stay that way:

1. Itere in all elements
2. If larger than five, print.
3. Itere in all elements AGAIN
4. Only if it is less than or equal to five, print.

This is a didactic response. In the practical case, several optimizations could be made, depending on the use of the data.

Answer 2

You can also treat the arrays before printing, as follows:

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
asort($numeros); // necessário se o array estiver desordenado
$num = 5; // valor limite
$pos = array_search($num,$numeros); // pega a posição do array conforme valor determinado
$numerosMenores = array_slice($numeros,0,$pos); // pega parte do array com os numeros menores
$numerosMaiores = array_slice($numeros,$pos); // pega parte do array com os numeros maiores
$numeros = array_merge($numerosMaiores, $numerosMenores); //funde os arrays

foreach($numeros as $numero){
    echo '<li>'.$numero.'</li>';
}
echo '</ul>';

OBS: If your array is out of order you will first need to order it, asort($numero), or this won’t work.

Answer 3

Although with PHP you can do many things in many different ways it doesn’t mean you will hammer a bolt just because you haven’t found the right key.

With that in mind, analyze what you want to do: "A condition within an iteration". What will that condition do? " It will filter a certain result before performing the routine on it".

So use the right or most appropriate tool for the task at hand: array_filter()

This function will receive a given input array and filter it according to the function passed as the second argument. This function can be a string for some function known to the program (such as a native function, for example), an anonymous function, or even an object method.

$data = array( 1,2,3,4,5,6,7,8,9,10 );

$data = array_filter(

    $data,

    function( $current ) {

        return ( $current <= 5 );
    }
);

$date, now has only five elements, from one to five.

"But I have to print everything"

Here is where the various possibilities come in. A cool thing would be to compute the difference of the input array for this filtered, with array_diff()

"But still I’ll have to iterate to print"

Only if you want to. Because a one-dimensional matrix can perfectly be printed with implode(), with HTML and everything:

$data = array( 1,2,3,4,5,6,7,8,9,10 );

$lowerThanFive = array_filter(

    $data,

    function( $current ) {

        return ( $current <= 5 );
    }
);

printf(

    "<ul>\n    <li>%s</li>\n</ul>",

    implode( "</li>\n    <li>", $lowerThanFive )
);

printf(

    "\n\n<ul>\n    <li>%s</li>\n</ul>",

    implode( "</li>\n    <li>", array_diff( $data, $lowerThanFive ) )
);

Note that, because this is an example, I created two distinct, unordered lists, mainly to demonstrate that it works.

Answer 4

Instead of displaying inside the foreach, store these values within a string and when you finish the look print the biggest $and then the lowest $

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
$maiores='';
$menores='';
echo '<ul>';
foreach($numeros as $numero){
if($numero > 5){
    $maiores.= '<li>'.$numero.'</li>';
}else{
    $menores.= '<li>'.$numero.'</li>';
  }
}
echo $maiores;
echo $menores;
echo '</ul>';

Answer 5

A simpler way to solve this, taking into account that the important thing is to select from the largest to the smallest and gain performance:

$numeros = array(1, 2, 3, 4, 5, 6, 7, 8, 9);
rsort($numeros);

foreach($numeros as $numeroSelecionado)
{
    echo $numeroSelecionado.'<br/>';
}