To compare PHP strings, you should choose different methods according to your needs, and you cannot blindly use ==. Strictly compare it with ===, and strcmp() is used for dictionary order comparison. 1. == is unreliable, and will perform type conversion, resulting in unexpected results, such as '0e123' == '0' is true; 2. === is the safest comparison method, and the judgment is completely consistent and the type is not converted; 3. strcmp() is used to compare strings in dictionary order, returning -1, 0, and 1 to represent size relationships, and is case sensitive; 4. Safe scenarios must avoid ==, and === is better in performance. Pay special attention to traps when comparing null or boolean values.

When comparing strings in PHP, many people are confused about using strcmp() function or the == operator. In fact, the behaviors of the two are not exactly the same, and there are differences in usage scenarios.

To put it directly into the point: If you are going to do a strict string comparison, you should prioritize other methods rather than == . And strcmp() has its scope of application, but it is not omnipotent.

1. == is not a real "string comparison"

You may think that writing 'abc' == 'abc' is a string comparison, but in some cases, PHP's == will do something unexpected.

For example:

 '0e123' == '0' // Return true

This is because in loose comparisons, PHP tries to convert strings to numbers. If both sides look like scientific notation (such as starting with 0e ), they are treated as floating point numbers, and the result is 0 == 0 .

So, when you want to compare if two strings are literally the same , == is not reliable.

2. === is a safer alternative

If you just want to determine whether the two strings are exactly the same (including case, character order, length, etc.), you should use === , which will not perform type conversion.

for example:

 'abc' === 'abc' // true
'0e123' === '0' // false

This comparison method is more intuitive and easier to understand than strcmp() . Especially when verifying user input or sensitive data (such as password hash), it is necessary to use strict comparison.

3. The purpose of strcmp() : sorting and case sensitivity

So what does strcmp() do? It is mainly used to compare strings in dictionary order , returning an integer value to represent the size relationship between two strings:

• Return value < 0: The first string is smaller than the second
• Return value = 0: Two strings are equal
• Return value > 0: The first string is greater than the second

For example:

 strcmp('apple', 'banana') // -1
strcmp('hello', 'hello') // 0

This function is useful when sorting, searching, or when you need to know the order of strings. And it is case sensitive, that is, 'Apple' and 'apple' will be considered different.

There is also a case-insensitive version that is strcasecmp() , which can be selected as needed.

4. Small details on safety and performance

• Security : Do not use == to compare password hash or tokens, because you may encounter magic hash problems, resulting in wrong matches.
• Performance : === is usually faster than strcmp() because it does not require calculating the string order, it only needs to determine whether it is completely consistent.
• Note the null trap : == can produce strange results if one of the operands is null or boolean. For example, 'abc' == null is true , but 'abc' === null is a reasonable judgment.

Basically that's it. You can decide which method to use according to actual needs:

• Decision is exactly consistent → ===
• Requires dictionary order → strcmp()
• Comparison of case-insensitive order → strcasecmp()
• Never use it in sensitive occasions ==

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