1. Arrays (6624/-)
2. Assignment statements (4300/-)
3. Associative Arrays (4754/-)
4. Case-Sensitivity (5340/-)
5. Comments (6137/-)
6. Common string constants (4421/-)
7. Create thumbnails using PHP (12105/-)
8. Dates (5973/-)
9. End of statement (4192/-)
10. Equality (3414/-)
11. For loops (4152/-)
12. Get a user's IP address (10371/-)
13. HTML encoding functions (6694/-)
14. If statements (5275/-)
15. Loosely Typed Variables (3803/-)
16. MySQL - 'INSERT..SELECT' copies data from a SELECT into a table (12180/-)
17. MySQL - Adding or Subtracting days (8424/-)
18. MySQL - Components of a date (5721/-)
19. MySQL - Concatenate strings (48750/-)
20. MySQL - Conditional values (17533/-)
21. MySQL - CREATE a new table (6461/-)
22. MySQL - Delete (12142/-)
23. MySQL - DROP an unwanted table (5106/-)
24. MySQL - Explicitly enter a NULL (4406/-)
25. MySQL - Find the Insert ID (6283/-)
26. MySQL - Finding a substring in a string (15938/-)
27. MySQL - Finding out your tables (4310/-)
28. MySQL - Format dates (10884/-)
29. MySQL - Formatting numbers to two decimal places (16582/-)
30. MySQL - Get the 11th to the 20th rows of the Squeek table - by UserName (4959/-)
31. MySQL - Get the date and time right now (9092/-)
32. MySQL - Get the first 10 rows of the Squeek table (5016/-)
33. MySQL - Insert (14207/-)
34. MySQL - Insert a date (22909/-)
35. MySQL - Joining two tables (11758/-)
36. MySQL - Match a range of dates (9193/-)
37. MySQL - Match a specific date (4914/-)
38. MySQL - Replace a NULL with a specific value (12870/-)
39. MySQL - Select - including strtolower() (12579/-)
40. MySQL - Select random row (27545/-)
41. MySQL - SELECT within SELECT (28906/-)
42. MySQL - Substring: Extracting part of a string (23520/-)
43. MySQL - Update (11996/-)
44. MySQL - uppercase / lowercase (14963/-)
45. MySQL - What are the columns of the Squeek table? (3985/-)
46. Need to declare variables? (5224/-)
47. PHP - Random Number (16283/-)
48. PHP - Sending Email (9912/-)
49. Print 1 to 10 on a web page (4886/-)
50. Regular Expressions (4798/-)
51. Script Tags (4794/-)
52. Sending HTML to Browser (3810/-)
53. String Concatenation (9683/-)
54. String Evaluation (4863/-)
55. Strings (3792/-)
56. Switch/Case (4236/-)
57. True and False (3510/-)
58. Variables (3310/-)
59. While statements (3765/-)

Yes, variables embedded in strings are evaluated if string delimited by double-quotes.

$a = "A";
$b = "$a B";
/* now $b == 'A B' */