PHP5 String Performance: Inline vs. Concatenation – Which is Faster?

Performance Comparison: Inline Strings vs. Concatenation in PHP5

In PHP5, it is possible to embed strings directly into code using inline string syntax ($foo) or use concatenation operators (. and .=) to combine strings. However, are there significant performance differences between these approaches?

Consider the following code samples:

$foo = 'some words';

// Case 1: Inline string
echo "these are $foo";

// Case 2: Curly brace concatenation
echo "these are {$foo}";

// Case 3: Dot concatenation
echo 'these are ' . $foo;

Inline Strings vs. Curly Brace Concatenation

Previously, there was a minor performance difference between inline strings (case 1) and curly brace concatenation (case 2). Inline strings were slightly faster. However, since PHP5.4, both methods have been optimized, and there is no longer a noticeable performance gap.

Concatenation vs. Dot Concatenation

The main performance difference lies between concatenation operators (.) and dot concatenation (case 3). Dot concatenation is typically slower than concatenation operators because it involves string concatenation at runtime. Concatenation operators, on the other hand, create a single string in memory without the need for runtime concatenation.

Benchmark Results

Measurements have shown that dot concatenation is significantly slower than concatenation operators, with a noticeable difference even for relatively short strings.

Conclusion

For optimal performance in PHP5, use concatenation operators for string concatenation. While inline strings and curly brace concatenation provide convenience, they do not offer a performance advantage. Remember that performance measurements should be conducted on your specific codebase, as results may vary depending on other factors.

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