When using the if/else control structure for conditional judgment in PHP, the following points should be followed: 1. Use if/else when different code blocks need to be executed according to the conditions; 2. Execute if branches if the condition is true, enter else or else if; 3. When multi-conditional judgment, else if should be arranged in logical order, and the range should be placed in front of the front; 4. Avoid too deep nesting, it is recommended to consider switch or reconstruction above three layers; 5. Always use curly braces {} to improve readability; 6. Pay attention to Boolean conversion issues to prevent type misjudgment; 7. Use ternary operators to simplify the code for simple conditions; 8. Merge and repeat judgments to reduce redundancy; 9. Test boundary values to ensure the complete logic. Mastering these techniques can help improve code quality and stability.
When writing PHP, the control structure is the most basic and commonly used part. If/Else is one of them, used to make conditional judgments and determine how to proceed with the program. It is not difficult to understand it, but it takes some experience to use it well.
When to use if/else?
If/else comes in handy when you need to execute different code blocks based on a certain condition. For example, after the user logs in, jumps to different pages, displays different content according to different roles, etc.
- If the condition is true (true) executes the code in if
- If the condition is false, enter else or else if you judge other situations
For example: If the user level is greater than or equal to 5, you can make a post like this:
if ($user_level >= 5) {
echo 'can post';
} else {
echo 'Insufficient permission';
}In actual development, this kind of logic is very common, such as checking whether the form input is empty, judging payment status, etc.
How to arrange Else if?
Sometimes there are more than two conditions, and else if is required. The order is very important at this time, because once a certain condition is met, the subsequent one will not be judged again.
For example, rating according to different scores:
if ($score >= 90) {
echo 'A';
} elseif ($score >= 80) {
echo 'B';
} else {
echo 'C or lower';
}A few points to note:
- The order of conditions cannot be chaotic, and the range is large and placed in front
- Finally, use else to handle the situation
- Avoid nesting too deep, more than three layers, it is recommended to consider switch or refactor logic
Tips and precautions for use
Some details are easily overlooked, but affect readability and stability:
- Bracelets are not allowed : Even if there is only one line of code, it is recommended to add curly braces
{}to avoid errors in subsequent expansions. - Boolean value judgments should be accurate : like
0, empty string'', andnullare all considered false in judgment, so pay attention to the variable type. - Simplified conditional expressions : For example,
$is_logged_in ? '歡迎' : '請(qǐng)登錄'can replace simple if/else with ternary operators. - Avoid repeated judgments : If multiple conditions handle the same logic, merge judgments reduce redundant code.
In addition, remember to test the boundary value after writing, such as the case where it just equals the critical value to prevent some cases from being missed.
Basically that's it. Mastering if/else is the first step in writing a PHP control process. After using it proficiently, you will find that many places can be flexibly applied.
The above is the detailed content of PHP Control Structures: If/Else. For more information, please follow other related articles on the PHP Chinese website!
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