Recommended articles about php FILTER_CALLBACK() function

Ask the experts how to understand the code? Doesn’t array_filter require array_filter(array,function)? Does writing the array directly mean that the value of the custom function is zero? Or how to understand? Please give me some advice------Solution--------------------array array_filter (array [, callback callback] ) array_filter() sequentially filters each element in the array array. A value is passed to the callback function. If the callback function returns TRUE, the current value of the array array will be included in the returned result array. The key names of the array remain unchanged. If no callback function is provided, array_filter() will delete all entries in the array whose equal value is FALSE. The equal value of false is empty, false, 0... ------Solution---------

1. How to understand the code? array_filter

#Introduction: Ask the experts how to understand the code? array_filterarray_filter(array,function) is not required ? Does writing the array directly mean that the value of the custom function is zero

2. Please tell me what function to use to get the number of key values ​​in the array that are not empty

Introduction: What function should I use to get the number of key values ​​in the array that are not empty? For example array: Array ( [0] => aa [1] => bb [2] =>

##3. What function should I use to get the number of key values ​​in the array that are not empty? ##Introduction: What function should be used to obtain the number of key values ​​in the array that are not empty? For example, array: Array( [0] => aa [1] => bb [2] => cc&nbs

4. How to understand the above code? array_filter

##Introduction: Ask an expert how to understand the code? array_filterIsn’t array_filter(array,function) needed? Does writing the array directly mean that the value of the custom function is zero

5.

PHP filter example

##Introduction:?php function convertSpace($str) { return str_replace(' ', '_', $str); } $ str = 'i am a great guy!'; echo filter_var($str, FILTER_CALLBACK, array('options'='convertSpace')); echo filter_var($str, FILTER_CALLBACK, array('options'='strtouppe

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