A friend recently asked me about the meaning of Psalm 24:7. Its one of my favorite Psalms - I will never forget when my mentor, Dr. Martin Massinger, "opened" it up for me. The margin notes in my Bible help me recall his words:
Psalm 24:7 is part of a trio of Psalms about the Messiah (Messianic psalms). Taken together they describe in many ways the life of Christ.

In Psalm 22, the events of the cross are clearly in view, and David uses figures that describe or predict the agonies of Christ. Psalm 22:1 prophesies Christ’s cry on the cross, bearing the sins of the world. Verse 7 describes the passers-by who ridiculed Him (Matt. 27:39). Verse 8 prophesies the actual words of those hurling insults at Him (Matt. 27:43). Verse 16 prophesies the piercing of Christ’s hands and feet (John 20:25). Verse 17 indicates that none of Christ’s bones would be broken (John 19:33–36). Psalm 22:18 prophesies the soldiers gambling for Christ’s clothes (John 19:24). Psalm 22:24 prophesies Christ’s prayer to the Father concerning His impending death (Matt. 26:39; Heb. 5:7).1

Psalm 23 is most familiar - the Shepherd Psalm.

Psalm 24:7–10 depicts the victorious, returning king triumphantly entering Jerusalem to rule. The "near" event that it was composed for was probably the installation of the Ark of the Covenant in the Temple built by Solomon. The gates and doors are probably the gates of Jerusalem and the doors of the Temple. David uses personification to show that everything is anticipating the future installation of the rightful King. It may (this is my opinion) be related to the verse that says the stones will cry out if the crowd does not - but that's just my opinion. I think of the talking trees in Narnia and imagine that's the way CS Lewis thought of it, though I don't have any evidence this is what he had in mind......

Taken together, the 3 Psalms can be thought of like this:
22 - the Past, Jesus' cross where He is our Savior and showed Himself to be truly the Good shepherd, willing to lay down His life for the sheep (John 10:11)

23 - the Present, where the Great Shepherd knows all our trials and lovingly uses His crook (shepherd's staff) to guide and correct us. Heb 13:20)

24 - the Future, where the Chief Shepherd will wear the crown He so richly deserves. (1 Peter 5:4)