Common mistakes in PHP

This article mainly shares with you the common mistakes in PHP, which are summarized when using PHP in daily life. I hope it can help everyone.

1 Quoted question

<?php$arr = range(1,3);foreach ($arr as &$v){
}


print_r($arr);foreach ($arr as $v){
    print_r($arr);

}

2 Detecting whether a variable is set

<?php$data = array();//$data[&#39;name&#39;]  = 0;//$data[&#39;name&#39;]  = null;$data[&#39;name&#39;] = false;if (isset($data[&#39;name&#39;])) {
    var_dump(&#39;not set name&#39;);
} else {
    var_dump(&#39;already set name&#39;);

}if (($data[&#39;name&#39;])) {
    var_dump(&#39;data-name 存在&#39;);
} else {
    var_dump(&#39;data-name 不存在&#39;);

}if (array_key_exists(&#39;name&#39;, $data)) {
    var_dump(&#39;key name 存在于array中&#39;);
} else {
    var_dump(&#39;key name 不存在于array中&#39;);

}

Three values, three ways to determine whether a variable exists The results are:

3 Directly use the data index returned by the function

<?phpclass Config{
    private $values = [];    public function __construct() {
        // 使用数组对象而不是数组
        // $this->values = new ArrayObject();
    }    public function &getValues() {
        return $this->values;
    }
}$config = new Config();$config->getValues()[&#39;test&#39;] = &#39;test&#39;;echo $config->getValues()[&#39;test&#39;];

If you do not use object to store values, or do not use a reference to turn the result of the function into a reference to the values ​​array, then it may be wrong

Notice: Undefined index: test in /Users/leon/Documents/workspace/test/php7.php on line 20

This will destroy the encapsulation of the object, it is best to write like this

class Config{
    private $values = [];    public function setValue($key, $value) {
        $this->values[$key] = $value;
    }    public function getValue($key) {
        return $this->values[$key];
    }
}$config = new Config();$config->setValue('testKey', 'testValue');echo $config->getValue('testKey');    // 输出『testValue』

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