How to query elements in the same array using PHP

PHP is an object-oriented server-side scripting language, which is very suitable for developing server-side Web applications. Arrays are a very important data type in PHP that allow multiple values ​​to be grouped together and referenced and manipulated as a single variable. In the process of using arrays, we often encounter situations where we need to query elements in the same array. This article will introduce how to use PHP to query elements in the same array.

1. Use loop traversal to query

PHP provides a variety of loop statements that can be used to traverse the elements in the array and perform query operations. Here we introduce two commonly used loop statements:

1.1 for loop

The for loop is a commonly used loop statement that can be used to traverse elements in an array. The following is a sample code that uses a for loop to query elements in the same array:

<?php $array = array(1, 2, 3, 4, 1, 3);
$len = count($array);
for ($i = 0; $i < $len; $i++) {
    for ($j = $i + 1; $j < $len; $j++) {
        if ($array[$i] == $array[$j]) {
            echo "相同的元素为：".$array[$i]."<br />";
        }
    }
}
?>

In the above code, we first define an array containing repeated elements $array, and then use a for loop Iterate through all the elements in the array and for each element we again use a for loop to find the element that is the same as it. If the same element is found, the element is output.

1.2 foreach loop

The foreach loop is also a commonly used loop statement, which can be used to traverse the elements in the array and perform query operations. The following is a sample code that uses a foreach loop to query elements in the same array:

<?php $array = array(1, 2, 3, 4, 1, 3);
$count = array_count_values($array);
foreach ($count as $key => $value) {
    if ($value > 1) {
        echo "相同的元素为：".$key."<br>";
    }
}
?>

In the above code, we first define an array containing repeated elements $array, and then use the PHP built-in Function array_count_values counts the number of occurrences of each element in the array, and stores the statistical results in the associative array $count. Finally, we use a foreach loop to traverse the $count array and determine whether the number of occurrences is greater than 1. If it is greater than 1, the element will be output.

2. Use PHP built-in function query

In PHP, there are multiple built-in functions that can be used to query elements in the same array. Below we introduce two commonly used functions:

2.1 array_count_values

array_count_values ​​function can be used to count the number of occurrences of each element in an array and store the statistical results in an associative array. The following is a sample code that uses the array_count_values ​​function to query elements in the same array:

<?php $array = array(1, 2, 3, 4, 1, 3);
$count = array_count_values($array);
foreach ($count as $key => $value) {
    if ($value > 1) {
        echo "相同的元素为：".$key."<br>";
    }
}
?>

In the above code, we first define an array containing repeated elements $array, and then use the PHP built-in Function array_count_values counts the number of occurrences of each element in the array, and stores the statistical results in the associative array $count. Finally, we use a foreach loop to traverse the $count array and determine whether the number of occurrences is greater than 1. If it is greater than 1, the element will be output.

2.2 array_unique, array_diff_assoc and array_diff_key

The array_unique function can be used to remove duplicate elements from an array and return the array after removing duplicate elements. The array_diff_assoc and array_diff_key functions can be used to compare the difference between two arrays and return different elements. By using these functions, we can also query elements in the same array. The following is a sample code:

<?php $array = array(1, 2, 3, 4, 1, 3);
$unique = array_unique($array);
$diff = array_diff_assoc($array, $unique);
foreach ($diff as $key => $value) {
    echo "相同的元素为：".$value."<br>";
}
?>

In the above code, we first define an array containing repeated elements$array, then use the array_unique function to remove duplicate elements in the array, and store the result in the $unique variable. Then we use the array_diff_assoc function to compare the difference between the two arrays and store the different elements into the $diff variable. Finally we use foreach to loop through the $diff array and output the same elements.

Summary

The above is how to query elements in the same array in PHP. We can easily implement this function by using loop statements, built-in functions and other methods. In actual development, you can choose a method that suits you for query operations. At the same time, it should be noted that repeated elements may have an impact on the performance of the program, so in actual development, you should try to avoid repeated elements in the array.

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