"PHP Core – Part 1 – Understanding Variables Types", Denys Kurasov

Talk on data types and how PHP works with them at the core level with use cases for more efficient utilization.

1. Денис Курасов PHP CORE – ЧАСТИНА 1 – ТИПИ ЗМІННИХ PHP fwdays

2. About Myself Lead PHP developer at Growe Over 8 years of experience in backend development Passionate about computer science Experienced in embedded development, gained through university projects, including creating a self-driving robot Football is in my heart

3. What is variable?

4. Types in core

5. Zval

6. Zend value

7. Integer zend_long Represents int64_t int32_t -2147483648 -9223372036854775808 8 bytes 4 bytes Max Min 2147483647 9223372036854775807 Memory In C Actual Memory 12 bytes 1 6 bytes 64 bit 32 bit

8. Integer - Integer In Memory

9. Integer - Integer Overflow

10. Float | Double | Real double 4 bytes Max Min Memory In C 1.7976931348623157E+308 2.2250738585072014E-308 float 1.17549435 E-38 3.4028235 E +38 8 bytes Actual Memory 12 bytes 16 bytes 64 bit 32 bit

11. Float - IEEE754 V = (-1) s * M * 2 E 536870912000000 1111010000100100000000000000000000000000000000000 01010111111101000010010000000000 1.907348*2 48 M E

12. Float - IEEE754 Float 32 bits 0.1640625 1.120393e-38 INF NaN

13. Float - Round-off error

14. Float - Mistakes that are worth lives 25 Feb 1991 (0.000110011001100110011001) 2 (0.099999964237213134765625) 10 0.1 - 0.099999904632568359375 = 9.54 * 10 -8 sec 9.54 * 10 -8 * 10 * 60 * 60 * 100 = 0.34344 sec Error after working 100 hours Error 2000 * 0.34344 = 687 metres (0.1) 10 ≈

15. Float - Comparing Floats

16. Float - Dangerous operations with Float

17. Boolean IS_TRUE 1 byte Actual Memory Memory In C (PHP Core) 1 byte 16 bytes 64 bit 16 bytes 64 bit IS_FALSE

18. Array

19. Array Data Layout

20. INVALID_IDX NULL 1 1 1 INVALID_IDX 2 -1 -2 -4 1 2 3 -3 Key Val

21. INVALID_IDX INVALID_IDX INVALID_IDX NULL NULL NULL NULL key1 DJBX33A hash fn 6385400191 6385400191| -4 -1 1 key2 DJBX33A hash fn 6385400192 6385400192 | -4 -4 1 1 key3 DJBX33A hash fn 6385400193 6385400193 | -4 -4 INVALID_IDX 2 -1 -2 -4 1 2 3 -3 Key Val

22. INVALID_IDX NULL 1 1 1 INVALID_IDX 2 -1 -2 -4 1 2 3 -3 Key Val UNDEF

23. Array – Memory

24. SPL Fixed Array

25. String PHP string in core Define string in C

26. String - UTF-8, how?

27. String - Interned Strings

28. String - Concatenation

29. Questions? Thank you for watching