Question 40422 in PHP Question posted in
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variables should be passed by reference error in php

I am using php 7. I have a php code as shown below in which when user enters all 5 values in both text fields at Line B and Line C and hit the save button at Line D, I am
getting the error "Only variables should be passed by reference at Line A".

The goAhead() method is inside the class SapDiagram in def.php file below.

abc.php

<?php
$diagram = &$_SESSION['sap']->diagrams[$index];

if ('POST' == $_SERVER['REQUEST_METHOD']) {
    for ($i = 0, $used = 0; 5 > $i; ++$i) {
        if (!empty($_POST["normal$i"]) && !empty($_POST["wrap$i"])) {
            $diagram->goAhead(new SapFile($_POST["normal$i"], $_POST["wrap$i"]), $used++);  // Line A
        }
    }
}

?>
<html>
<head>
    <title>Good World</title>
</head>
<body>
<form method="post" action="<?php echo $_SERVER['PHP_SELF']; ?>">
    <?php
    for ($i = 0; 5 > $i; ++$i) {
        ?>
        <fieldset>
            <input type="text" name="normal<?php echo $i; ?>"
                   value="<?php echo isset($diagram->files[$i]) ? $diagram->files[$i]->normal : ''; ?>"/>    <!-- Line B -->
            <input type="text" name="wrap<?php echo $i; ?>"
                   value="<?php echo isset($diagram->files[$i]) ? $diagram->files[$i]->wrap : ''; ?>"/>  <!-- Line C -->
        </fieldset>
        <?php
    }
    ?>
    <div class="submit">
        <input type="submit" value="Save"/>  <!-- Line D -->
        <input type="reset"/>
    </div>
</form>
</body>
</html>

def.php

class SapDiagram
{
    public $files;
    
    public function goAhead(&$file, $index = null)
    {
        if (is_null($index)) {
            $index = sizeof($this->files);
        }

        $this->files[$index] = $file;
    }
}

Problem Statement:

I am wondering what changes I need to make at Line A and or inside the goAhead method in order to avoid this error.

Note: goAhead() method is being used at many places in the code so I believe removing & is not the solution.

Tags:

2

Answers


  1. 0

    See the manual: …no other expressions should be passed by reference, as the result is undefined. For example, the following examples of passing by reference are invalid:

    foo(new Foobar()) // Produces a notice as of PHP 7.0.7
                  // Notice: Only variables should be passed by reference

    https://www.php.net/manual/en/language.references.pass.php

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  2. 0

    When you define your function as goAhead(&$file, ...), that & is a Pass By Reference, which is not compatible with something like goAhead(1, ...) or goAhead(new ..., ...), etc.

    To solve this, read your error and pass a variable.

    Only variables should be passed by reference …

    Instead of

    $diagram->goAhead(new SapFile($_POST["normal$i"], $_POST["wrap$i"]), $used++);

    Define a variable and use that:

    $file = new SapFile($_POST["normal$i"], $_POST["wrap$i"]);
$diagram->goAhead($file, $used++);

    So all in all:

    if ($_SERVER['REQUEST_METHOD'] == 'POST') {
    for ($i = 0, $used = 0; 5 > $i; ++$i) {
        if (!empty($_POST["normal{$i}"]) && !empty($_POST["wrap{$i}"])) {
            $file = new SapFile($_POST["normal{$i}"], $_POST["wrap{$i}"]);
            $diagram->goAhead($file, $used++);
        }
    }
}
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