What should I do if the performance of loop traversal and combination of data retrieved from the database is poor?-PHP Tutorial-php.cn

What should I do if the performance of loop traversal and combination of data retrieved from the database is poor?

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Release： 2016-08-04 09:19:02

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Requirement: Statistics of daily data based on start and end time
The current data retrieved from the database has about 10 two-dimensional arrays with the same structure as follows:

<code>[
    '0' => [
        'time' => '2016-8-3',
        'data1'=> 'xxx',
        ...
    ]
]</code>

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Because each array has required fields, these 10 two-dimensional arrays need to be combined. The idea is as follows:
Traverse and retrieve data based on date

<code>while (strtotime($start_time) < strtotime($end_time)) {
    
    // 10个foreach
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    ...

    $start_time = strtotime($start_time . ' +1 day');
    
}</code>

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The final data structure I want to combine:

<code>[
    '2016-8-3' => [
        'data' => '',
        ...
    ],
    
    '2016-8-4' => [
        'data' => '',
        ...
    ]
    ..
]</code>

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But it seems that the performance of that while is very poor, and the data cannot be run out. After waiting for a long time, it directly prompts:
Maximum execution time of 30 seconds exceeded
Do you have any good suggestions?

Reply content:

Requirement: Statistics of daily data based on start and end time
The current data retrieved from the database has about 10 two-dimensional arrays with the same structure as follows:

<code>[
    '0' => [
        'time' => '2016-8-3',
        'data1'=> 'xxx',
        ...
    ]
]</code>

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Because each array has required fields, these 10 two-dimensional arrays need to be combined. The idea is as follows:
Traverse and retrieve data based on date

<code>while (strtotime($start_time) < strtotime($end_time)) {
    
    // 10个foreach
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    
    foreach($arr as $k => $v) {
        if (strtotime($start_time) == strtotime($v['time'])) {
            $data[] = $v[];
            ...
        }
    }
    ...

    $start_time = strtotime($start_time . ' +1 day');
    
}</code>

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The final data structure I want to combine:

<code>[
    '2016-8-3' => [
        'data' => '',
        ...
    ],
    
    '2016-8-4' => [
        'data' => '',
        ...
    ]
    ..
]</code>

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There is something wrong with your loop, causing an endless loop. You can print out the $start_time and $end_time of each cycle. It must be strtotime($start_time) < strtotime($end_time)It will always be true